North Korea's nuclear missile will never be capable of reaching US: Donald Trump

President-elect Donald Trump has taken to Twitter to promise North Korea would not develop a nuclear missile capable of reaching US territory.

His comments come a day after the North Korean leader, Kim Jong-Un, appeared to try to put pressure on Trump by announcing his country is in the "final stages" of developing an intercontinental ballistic missile (ICBM).

"North Korea just stated that it is in the final stages of developing a nuclear weapon capable of reaching parts of the US," Trump tweeted last evening. "It won't happen!"

Although Washington has repeatedly vowed that it would never accept North Korea as a nuclear state, Trump has not previously clearly stated his policy on the isolated Stalinist state.

The Republican billionaire has already upended precedent by routinely taking to Twitter since his election last month to lambast critics and issue statements -- sometimes about the most serious national security issues -- sending analysts scrambling to divine what they may mean for US policy once he takes office on 20 January.

He launched a solo bid to restart the Cold War arms race last month, tweeting that the United States must "greatly strengthen and expand" its nuclear capabilities.

He has also angered China by tweeting accusations of military expansionism and currency manipulation.

But he will need Beijing, Pyongyang's closest ally, to deal with North Korea's mounting confrontation.

However, he appeared to complicate that prospect with his latest criticism last evening following his vow about North Korea.

"China has been taking out massive amounts of money & wealth from the US in totally one-sided trade, but won't help with North Korea," he tweeted. "Nice!"

In a 30-minute televised New Year's speech on Sunday, Kim said Pyongyang had "soared as a nuclear power," adding that it is now a "military power of the East that cannot be touched by even the strongest enemy."

Although he did not make a specific reference to the incoming Trump administration, he called on Washington to make a "resolute decision to withdraw its anachronistic hostile North Korea policy."

Analysts are divided over how close Pyongyang is to realising its full nuclear ambitions, especially as it has never successfully test-fired an ICBM.

However, North Korea carried out two nuclear tests and numerous missile launches last year in pursuit of its oft-stated goal -- developing a weapons system capable of hitting the US mainland with a nuclear warhead.

Thae Yong-Ho, North Korea's former deputy ambassador to Britain who defected to the South in August, has said Kim was planning a "prime time" nuclear weapons push in 2017 to take advantage of leadership transitions in Washington and Seoul.